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[laptime]

I have an '09 128i covertable that came with 205/55-16's

I'm swapping out rims/wheels with my 325ci (parts car) that has 225/50-17's

Wheels fit but only clear front shocks by a few mm.

What size spacers will work and are they different front and rear in order to keep the same width on both? ie: 15mm front 10mm rear?

preemptive Thanks!

[BMWCCA1]

Best guess would be to use spacers the same thickness as the difference between the offset of the two different sets of wheels.

For instance, let's assume your parts 325i is an original 17-in wheels and are marked 7x17 ET47.

And let's assume your 128i wheels are OE and marked 7x16 ET 44. The difference between 44 and 47 is 3mm.

You'll likely need a 3mm spacer, though 5mm or more would give you a wider stance. If you go much thicker you may need a hub-centric spacer and longer bolts. 3mm is about the smallest I've seen. 5mm or 10mm is more common. You could even go wider in the rear for a staggered look.

[laptime]

Thank you.
That’s exactly the type of information I needed.

I measured my wheelbase at:

67-3/4" front
69" rear

The rear is approx,32mm wider

Therefore, I'll install spacers @ 15mm front & 12.5mm rear

My Wheelbase will then be approx. 69" (-2mm) front and 70" rear

The 225/50-17's will take the place of the 205/55-16's without rolling fenders.

[Driven5]

Wheelbase is the distance from the font axle centerline to the rear axle centerline. Track is the distance from the left wheel centerline to the right wheel centerline. What you're talking about is effectively track.

I'm not following what your track and front vs rear track, has to do with determining offset/spacer fitment at either end, or how it's leading you to those particular spacer sizes. Also remember that your new tires are 1" larger diameter, so have a .5" larger radius, which will also affect fitment...Especially when the steering is turned.

[laptime]

Originally Posted by Driven5

Wheelbase is the distance from the font axle centerline to the rear axle centerline. Track is the distance from the left wheel centerline to the right wheel centerline. What you're talking about is effectively track.

I'm not following what your track and front vs rear track, has to do with determining offset/spacer fitment at either end, or how it's leading you to those particular spacer sizes. Also remember that your new tires are 1" larger diameter, so have a .5" larger radius, which will also affect fitment...Especially when the steering is turned.

Thank you for the knowledge.
I'm a bike guy so a lot of this is new to me as you can tell by my questions. But, I like these cars and am having fun tuning and dialing things for optimum performance.

[tsk94]

Exactly how much clearance do you have between the tire and the strut? Really, you only need a few mm's. If it's 5mm or more that's plenty. Even down to about 3-4mm is doable.

Spacers will obviously make the fitment easier for your peace of mind and aesthetically it will look better - but by the sounds of it it's not needed.